let arr = [ [ 'name', 'csc' ], [ 'age', '18' ], [ 'arr', [ 1, 2, 3 ] ] ]

Object.prototype.myFromEntries = function(arr) {
    let obj = {}
    arr.forEach(item => {
        obj[item[0]] = item[1]
    })
    return obj
}

let a = Object.myFromEntries(arr)
console.log(a);